CVE-2026-52761: ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx

Routine

MEDIUM 5.8REMOTEWATCHLISTUPGRADE

CVE-2026-52761 is a medium-severity flaw (CVSS 5.8) affecting modsecurity. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 through 3.0.15, the t:utf8toUnicode transformation in src/actions/transformations/utf8_to_unicode.cc produces wrong output on i386 architecture because snprintf uses sizeof on a char pointer rather than the length of the unicode buffer, allowing rules that use this transformation to be bypassed on i386 architecture. This issue

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-467
Published	2026-07-10
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: owasp

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-10 22:16 UTCPublished CVE record published
2026-10-25 15:10 UTCUpdated Record last modified

owasp modsecurity UPGRADE

Affected: >= 3.0.0 and <= 3.0.15

Fixed in: newer than 3.0.15

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy modsecurity || rpm -q modsecurity || modsecurity --version

2. UPGRADE to newer than 3.0.15 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade modsecurity

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade modsecurity

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison modsecurity sudo apt install modsecurity=<VERSION_BEFORE_3.0.0> sudo apt-mark hold modsecurity

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list modsecurity sudo dnf downgrade modsecurity-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add modsecurity

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-52761?

modsecurity: upgrade to newer than 3.0.15. Exact commands for each OS are on this page.

Is CVE-2026-52761 being exploited?

CVE-2026-52761 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-52761 affect?

CVE-2026-52761 affects modsecurity. Severity is medium (CVSS 5.8). ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 through 3.0.15, the t:utf8toUnicode transformation in src/actions/transformations/utf8_to_unicode.cc produces wrong ou

How urgent is CVE-2026-52761?

Priority 39/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities

Related CVEs

CVE-2026-52747 HIGH 8.6 UPGRADE ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx

References

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